Drill with a hard metal insert

ABSTRACT

For obtaining the maximum effectiveness from an axially extending drill with a hard metallic insert positioned on its drill end and a pair of axially extending oppositely spaced surfaces formed in its cylindrically shaped shaft, the ratio of the maximum diameter of its shaft to the dimension between the oppositely disposed surfaces is in the range of 1 : 0.7 to 1 : 0.8.

United States Patent 1 Imelmann et al.

DRILL WITH A HARD METAL INSERT Inventors: Wilfried lmelmann, Vaduz;Siegfried Benedic, Eschen, both of Liechtenstein Assignee: l-liltiAktiengesellschaft, Schaan,

Liechtenstein Filed: June 10, 1971 Appl. No.: 151,823

Foreign Application Priority Data Jan. 16, 1973 [56] References CitedUNITED STATES PATENTS 2,360,385 l0/l944 Anderson ..4()8/59 PrimaryExaminer-Francis S. Husar Attorney-Town and McGeady [5 7 ABSTRACT Forobtaining the maximum effectiveness from an axially extending drill witha hard metallic insert positioned on its drill end and a pair of axiallyextending oppositely spaced surfaces formed in its cylindrically June12, 1970 Germany ..P 20 29 047.5 Shaped h the ratio of the maximumdiameter of its shaft to the dimension between the oppositely US. Cl...408/226, 408/144, 408/229 disposed Surfaces is in the range of 1 a 0to l I 0.8 Int. Cl. ..B23b 51/00 Field of Search ..408/l44, 199, 226,227, 229, 2 Claims, 3 ng F g r 7 I 1 i l l i D a j l 4 W1 5 1PATENTEDJAH 15 I975 Fig. 2

ATTORNEY 1 DRILL WITH A HARD METAL INSERT SUMMARY OF THE INVENTION Thepresent invention is directed to a drill having a hard metallic insertpositioned on its drill end and a pair of oppositely disposedsurfacesformed in the cylindrical shaft of the drill and, more particularly, itis directed to the dimensional relationship between the diameter of thecylindrical shaft and the spacing between the oppositely disposedsurfaces on the shaft.

Drills are known which have axially extending curved or plane surfacedgrooves extending along the drill shaft from its drill end to its shankend for discharging the cuttings or drillings from the drill end to theshank end of the drill. Such drills have the disadvantage that thecross-section of the drill is considerably weakened by the continuousgrooves formed along the drill shaft, particularly adjacent to thehighly stressed drill head, so that the effective or useful life of sucha drill is relatively short. To overcome this disadvantage, drills havebeen formed where the grooves are provided only in the shaft part of thedrill while its head has a full circular cross-section. In such anarrangement, the drill head is not weakened as indicated above, however,since the discharge of the drillings along the shaft is made moredifficult because of the absence of the grooves at the drill head, theuse of such a drill results not only in a reduced output but also inconsiderable heating of the drill head. The overheating of the drillhead has a harmful effect on the soldered seam of the hard metallicinsert.

Accordingly, the primary object of the present invention is to provide adrill which can be economically mass-produced while avoiding theabove-mentioned disadvantages.

Therefore, in accordance with the present invention, when using a drillwith a hard metallic insert positioned on its drill head or end, thegroove surfaces along the drill shaft are formed so that therelationship between the diameter of the shaft to the dimension betweenthe groove surfaces has a ratio in the range of l 0.7 to l 0.8.

In the above range which affords the optimum ratio between the drillshaft diameter and the spacing of its groove surfaces, the ratio islimited, on one hand, by the weakening of the drill shaft if a lessergroove surface spacing is employed and, on the other hand, by aninsufficient discharge of the drillings if a greater spacing between thegroove surfaces is used. Furthermore, a drill dimensioned within therange of the ratios set forth above has shown an increase in output ascompared to known drills.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawing and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is an elevational view of a drill formed in accordance with thepresent invention;

FIG. 2 IS a section taken along line Il-Il m FIG. I;

and

FIG. 3 is a graphic representation of the effective use of a drillformed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 a drill 1 is shownformed of an axially extending cylindrically shaped shaft 2 having adrill head end 4 and a shank end 5 with a shank 3 extending axially fromthe shank end. In the cylindrical shaft 2 a pair of oppositely disposedsymmetrically arranged plane surfaces 6a, 6b are provided which extendfrom the drill head end 4 to the shank end 5. As can be noted in FIG. 2,the plane surfaces 6a and 6b are in parallel relationship and are spacedapart by the dimension d. At the head end 4 of the drill, a hardmetallic insert 7 is positioned and the construction of the insert andthat of the drill head end is of a known type.

In FIG. 3 the results of tests are indicated showing the effectivenessof a drill compared with the relationship between the diameter D of thecylindrical shaft and the dimension or thickness d between the planesurfaces of the grooves in the cylindrical shaft. In the graphicrepresentation in FIG. 3, the ordinate indicates the effectiveness ofthe drill, that is a factor representing the drilling output and usefullife of the drill, and the abscissa represents the ratio between thethickness or spacing d of the groove surfaces and the diameter D of theshaft. The curve in FIG. 3 clearly shows that the optimum drill shaftdimensions prevail in the range of the ratio of d/D between 0.7 and 0.8.If the ratio or value d/D is greater than 0.8, that is, the spacingbetween the groove surfaces increases, it becomes considerably moredifficult to discharge the drillings along the length of the drillshaft. As a result, the drill output diminishes, the drill becomesoverheated, and the soldered seam of the metallic insert becomesdamaged. When the ratio falls below 0.7, the thickness dimension of theshaft between the groove surfaces is so small that the drill headbecomes weakened and its useful lifetime is substantially shortened.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the inventiveprinciple, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:

1. An axially extending drill having a substantially cylindricallyshaped shaft with a drill end and and shank end, a hard metallic insertpositioned on the drill end of said shaft, a pair of oppositely disposedsurfaces symmetrically arranged in said shaft and extending between thedrill end and the shank end thereof, the dimension between said surfacesbeing less than the diameter of said shaft, wherein the improvementcomprises that the ratio of the maximum diameter of said shaft to thedimension between the oppositely disposed said surfaces is in the rangeof I 10.7 to l 0.8.

2. An axially extending drill, as set forth in claim I, wherein saidsurfaces being planar and extending in parallel relationship to oneanother.

1. An axially extending drill having a substantially cylindricallyshaped shaft with a drill end and and shank end, a hard metallic insertpositioned on the drill end of said shaft, a pair of oppositely disposedsurfaces symmetrically arranged in said shaft and extending between thedrill end and the shank end thereof, the dimension between said surfacesbeing less than the diameter of said shaft, wherein the improvementcomprises that the ratio of the maximum diameter of said shaft to thedimension between the oppositely disposed said surfaces is in the rangeof 1 : 0.7 to 1 : 0.8.
 2. An axially extending drill, as set forth inclaim 1, wherein said surfaces being planar and extending in parallelrelationship to one another.